This application proposes to examine the role of the dopamine D3 receptor in propagating both the reinforcing and discriminative stimulus effects of cocaine through investigation of several different variables including individual variability, partial-agonist stimulation, and alternative training-schedule conditions. We will use a nonhuman primate model of both drug discrimination and self-administration. Using a chain schedule to combine drug discrimination with progressive-ratio self-administration, we will examine the relationships between cocaine dose, relative reinforcing strength, the production of discriminitive stimuli, and response to treatment with D3 partial-agonists using a within-subject design. By examining these relationships at the level of the individual, we hope to gain a better understanding of dopamine receptor mechanisms important to cocaine's abuse liability. Understanding the behavioral and neurochemical mechanisms that mediate cocaine reinforcement and exploring how individual differences may dictate responses to various pharmacotherapies are important objectives that will move the drug abuse field one step closer to providing effective, targeted treatment strategies able to combat cocaine addiction and abuse.